Structural Ply
Specialized polymer plies provide specific surface properties during the manufacturing of multilayer flexible packaging films. A coextruded matte layer is typically the outermost skin of a polyolefin structure, produced by extruding a blend of incompatible resins through a single die. This method ensures that the dull finish is integral to the film rather than applied as a secondary coating.
Surface Topography
Differential cooling rates between the blended polymers create a micro-textured surface that scatters light in multiple directions. This coextruded matte layer avoids the use of external matting agents that might otherwise migrate or rub off during high speed processing on a filling line. The resulting texture provides the necessary grip for pull belts in vertical form fill and seal machinery where slippery films would fail.
Such surfaces also prevent the blocking effect where smooth film surfaces cling together on the reel during storage in high humidity environments. The chemistry of the resin blend determines the depth and frequency of the surface peaks which are measured using gloss meters at various angles.
Optical Performance
Diffuse reflectance values define the quality of the finish and the clarity of the underlying print. A coextruded matte layer reduces specular gloss to levels below 20 gloss units at a 60 degree angle. This property remains consistent across the entire web width because the resin distribution is controlled at the extrusion die.
It allows for high contrast printing by reducing glare.
